【作者】 李瑞芳；

【导师】 吴广宁；

【作者基本信息】 西南交通大学 ， 高电压与绝缘技术， 2012， 博士

【摘要】 随着我国经济高速增长,电网不断向超/特高压、远距离、大容量的方向发展,输电线路雷电绕击防护问题日渐突出,受到了国内外的广泛关注。输电线路绕击特性的影响因素较多,如雷电活动规律及其特性参数、输电线路的结构参数、地形地貌等。目前有关雷电活动的规律,如先导发展过程的影响机理研究尚不完善；雷电流幅值概率是最重要的雷电特性表征参数之一,规程法给出的计算公式与实测值差异较大；不同地形地貌导致避雷线对导线的屏蔽作用不同,有关工作亟待开展；传统输电线路绕击率计算模型未考虑沿档距方向任意点导线高度的变化,计算结果和实际相比存在一定误差。因此,本文重点研究了雷电活动及地形地貌对输电线路绕击特性的影响,丰富了输电线路雷电屏蔽失效理论,对于线路雷电绕击的防护具有重要实用价值。论文围绕以下几个方面展开：研制了火花放电实验装置和放电路径辨识装置,分析了采用高速摄像机拍摄的放电图片,发现并阐述了短间隙火花放电的“阶段”现象,认为短间隙火花放电与雷电梯级先导发展过程存在相似性。研究了针电极间位置改变对放电次数的影响,通过对大量的试验数据进行拟合,找到了下电极被击概率随距离差变化的规律。建立了输电线路雷击模型,仿真研究了输电线路高度变化、电压极性对雷击概率的影响。调研了某地区2008年雷电活动分布,以该地区两条500kV输电线路为例,统计分析了各档距落雷数据。通过对比雷电流幅值概率分布的规程DL/T620-1997推荐公式计算结果和实测值,发现二者存在很大的差异。在CIGRE、IEEE Std等给出的雷电流幅值概率计算公式的基础上,通过近10年来雷电参数实测数据拟合得到雷电流幅值概率的计算公式,给出了系数β的变化范围和工程计算的推荐值。提出了以电气几何模型为基础的保护弧面、暴露弧面的概念,建立了三维电气几何模型。以导线的高度为变量,给出了绕击率随垂直于线路的截面与杆塔间距离的变化规律及计算式,通过将该计算式沿线路档距方向进行积分,得出单档距三维模型的雷电绕击率计算公式。研究了采用该计算公式后导线高度变化、保护角、雷电流幅值等因素的变化规律,并与电气几何模型做了对比分析。建立了山顶、山坡、从山脚到山顶架设等几种典型的输电线路架设方式下绕击跳闸率的分析模型,提出了这几种架设方式下输电线路绕击跳闸率的计算公式。以220kV双避雷线输电线路为例,研究了输电线路处于山脉不同位置时最大绕击雷电流和绕击跳闸率随地面倾角的变化规律。分析了单档距为跨谷地形时不同位置绕击特性的变化情况。更多还原

【Abstract】 Power grid is continuously developing toward Extra-high Voltage (EHV), long-distance and High-capacity with the high speed development of Chinese economy, thus the shielding failure protection issues of transmission line are gradually outstanding and have been widespread concern at home and abroad. Shielding failure characteristic of transmission line is under affected by many factors, such as, activity regularity and characteristic parameters of lightning, structure parameters of transmission line, topography and geomorphology, etc. At present, lightning activity regularity, such as influence mechanism of discharge selectivity is not sufficiently studied. The probability of lightning current amplitude is one of the most important parameters of characterization, while its calculation result from regulation method existing large difference compared with actual measured value. Different topography and geomorphology leads to the different shielding effect of shielded wire to conductor and this work is necessary to carry out. In addition, because the conductor height in arbitrarily point alone span direction is neglect, the error is existed between the calculation results of current shielding failure model of transmission line and actual data. Thus the key in this paper is to research how lightning activity and topography influence shielding failure characteristic of transmission line, which enriches the lightning shielding failure theory of transmission line and has important practical value for the lightning shielding failure protection. This paper commences around the following aspects:Test apparatus are made to produce spark discharge in short gap and identify spark paths. According to the analysis to some spark discharges photos which high-speed video camera take, several stages in spark discharge are discovered and cause of these phenomenons is explained. It also showed comparability of spark discharge and lightning discharge. Then a large number of experiments are fitted on the relationship between the location of point electrode and probability of discharge. The function relationship between the location and discharge probability of point electrode is obtained. Lightning model of transmission line is established, and the influence mechanism of height change of transmission line and voltage polarity to lightning probability is analysed.Lightning activity distribution in a certain area has been investigated and lightning strike condition of different span of two500kV transmission lines is analyzed. The distribution of lightning amplitude between actual data and calculation result of recommend formula in regulation DL/T620-1997is compared, and the data showns great difference between them. Formula about Probability of lightning current amplitude is fit based on recommend formulas of CIGRE、IEEE Std. and measured data about lightning parameters through the past10years. The effect of coefficient β on the formula on curves is analyzed and value range of coefficients is given.The concepts of protection globoidal and exposure globoidal are presented based on electro geometric model, and a three-dimensional electro-geometric model is built.The conductor height is made variable, change rules of shielding failure rate is obtained which changed with distance between the section vertical to transmission lines and tower. By means of integral to this formula, the formula about shielding failure rate of the whole span spatial model is obtained. The change regularities of conductor height variation, protection angle and lightning current amplitude by taking these calculation formulae are comparatively analyzed with electric geometry method (EGM).When transmission lines are installed on the following terrains, such as:the top of the hill, hillside and installed from the mountain foot to mountain top, model analysis model on transmission lines shielding failure trip-out rate is built. Calculation formulae for corresponding shielding failure trip-out rates are derived. Taking220kV transmission line with two overhead ground wires for example, both maximum shielding failure lightning current of transmission line located at different positions of the mountain range and the variation regularity of shielding failure trip-out rate with the dip angle of ground are researched. Finally, the change regularity of shielding failure performance at different positions of single span of transmission line is researched when single span is erected upon valley.更多还原